Magnetic response of the halo nucleus $^{19}$C studied via lifetime measurement
Abstract
The first lifetime measurement used to study the magnetic response of halo nuclei is presented. The lifetime
of the first excited state of the one-neutron halo nucleus 19C has been measured by two complementary
Doppler-shift techniques with the Gamma-Ray Energy Tracking In-beam Nuclear Array (GRETINA). The
B(M1; 3/2+ →1/2+g.s.) strength of 3.21(25)×10−3μ2
N determined for this decay represents a strongly hindered
M1 transition among light nuclei. Shell-model calculations predict a strong hindrance due to the near-degeneracy
of the s1/2 and d5/2 orbitals among neutron-rich carbon isotopes, while tensor corrections and loosely bound
effects are necessary to account for the remaining strength.